A Hall effect sensor is a device that varies its output voltage in response to changes in magnetic field, and are used in applications such as positioning and position detection, proximity switching, speed detection, current sensing, etc. Hall effect devices are often implemented in integrated circuit semiconductor devices.
Vertical Hall devices are used to measure magnetic field components parallel to the surface of semiconductor device embodying the sensor. Many different geometries are known for such devices, and they can be implemented through ordinary CMOS technologies. High voltage technologies increasingly make use of a highly conductive n-buried layer (nBL), which cannot be blanked out in the standard technology flow. This nBL can be problem for vertical Hall devices, because it shorts the bottom end of the Hall probe, decreasing magnetic sensitivity of the probe (magnetic sensitivity is the ratio of output voltage to magnetic field strength).